Unwrapping Plist and finding object - arrays

Question

Getting hugely frustrated trying to translate objective c to swift. I have the following code that works for objective c.
NSMutableArray *path = [NSMutableArray arrayWithContentsOfFile:[[NSBundle mainBundle] pathForResource:#"Sequence List" ofType:#"plist"]];
//Shuffle the array of questions
numberSequenceList = [self shuffleArray:path];
currentQuestion = currentQuestion + 1;
if (Round==1) {
//Take first object in shuffled array as the first question
NSMutableArray *firstQuestion = [[NSMutableArray alloc] initWithArray:[numberSequenceList objectAtIndex:0]];
//Find question and populate text view
NSString *string = [firstQuestion objectAtIndex:0];
self.lblNumber.text = string;
//Find and store the answer
NSString *findAnswer = [firstQuestion objectAtIndex:1];
Answer = [findAnswer intValue];
}
But I can't seem to get this to work in swift. I can pull out the contents of the plist using
var path = NSBundle.mainBundle().pathForResource("Sequence List", ofType: "plist")
But I can't see that there is an equivalent to objectAtIndex in swift. If I try the following I get an error message advising "string does not have a member named subscript", which apparently means I need to unwrap path.
let firstQuestion = path[0]

Answer 1

The methods you are calling, like NSBundle.mainBundle().pathForResource, return optionals, because they might fail. In Objective-C, that failure is indicated by a nil, whereas Swift uses optionals.
So in your example:
var path = NSBundle.mainBundle().pathForResource("Sequence List", ofType: "plist")
path is of type Optional<String> (or String?) and not of type String. Optional<String> doesn’t have a subscript method (i.e. doesn’t support [ ]). To use the string within, you have to check if the optional contains a value (i.e. the call to pathForResource was successful):
// the if let syntax checks if the optional contains a valid
if let path = NSBundle.mainBundle().pathForResource("Sequence List", ofType: "plist”) {
// use path, which will now be of type String
}
else {
// deal with pathForResource failing
}
You can read more about optionals in introduction of the Swift book.

Answer 2

You haven't translated the entire first line from Objective-C. You are missing the call to NSMutableArray which creates the array from the contents of the file. The original code is confusing because it calls the contents of the file path when it is really questions. Try this:
if let path = NSBundle.mainBundle().pathForResource("Sequence List", ofType: "plist") {
let questions = NSMutableArray(contentsOfFile: path)
//Shuffle the array of questions
numberSequenceList = self.shuffleArray(questions)
currentQuestion = currentQuestion + 1
if Round == 1 {
//Take first object in shuffled array as the first question
let firstQuestion = numberSequenceList[0] as NSArray
//Find question and populate text view
let string = firstQuestion[0] as NSString
self.lblNumber.text = string
//Find and store the answer
let findAnswer = firstQuestion[1] as NSString
Answer = findAnswer.intValue
}
}